The IP Multimedia Subsystem (IMS) is a reference architecture for the delivery of mobile and fixed IP-based services promulgated by the 3GPP consortium. IMS focuses on services and applications, enabling telephone companies, mobile operators, and other service providers to easily offer rich multimedia services over IP based networks as well as interface with legacy networks. At the highest level, the IMS architecture can be split into a transport plane, a control plane, and a service plane. Mobile devices or user equipment interface with the transport plane, while the control plane mediates signaling between user equipment and application servers that reside in the service plane to implement service related features.
In the drawings, like reference numerals denote like elements or features.